I want to make copy function file in UNIX - c

Question

when I input "./test test.c /home/user1/Desktop/" it doesnt work anything.
I want to make copy file from (now_path) to (other_path).
But, I dont know why it does not work I think it is perfect code. Is it has error or need some more other codes??
char ch;
int src, dst;
if( argc != 3 )
{
printf("argument error\n");
printf("usage: ./a.out src dest\n");
}
src = open( argv[1], O_RDONLY );
dst = open( argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644 );
while( read( src, &ch, 1 ))
write( dst, &ch, 1 );
close( src );
close( dst );
return 0;

Answer 1

It's impossible to figure out unless you start to check return values. The open function returns a negative value on failure, and errno is set to indicate what went wrong.
Same goes for read and write. They returns the number of bytes read/written and a negative value on failure. errno is also set by these functions.
You could use constructs like this:
if ((src = open( argv[1], O_RDONLY )) < 0) {
fprintf(stderr, "Error accessing source file.\n");
fprintf(stderr, "errno: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}

Answer 2

Your code is ok but you might want to ensure that the source file is readable before trying to copy it's content. Also you may want to terminate the program if an error occurs.
char ch;
int src, dst;
if( argc != 3 )
{
printf("argument error\n");
printf("usage: ./a.out src dest\n");
exit(1); // Terminate the program
}
if ((src = open( argv[1], O_RDONLY )) == -1)
{
printf("Error accessing source file.\n");
exit(1);
}
if (dst = open( argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644 )) == -1)
{
printf("Error accessing destination file.\n");
exit(1);
}
while( read( src, &ch, 1 ) > 0 )
write( dst, &ch, 1 );
close( src );
close( dst );
return 0;
Also, if the second argument will always be a directory, you'll need to set the open command for the destination file to the combination of the second and first arguments (argv[2] joined with argv[1]).
For this you can use the strcat function which copies the content of the second string into the first. Start by adding #include <string.h> to the header of your program:
char* buffer[BUF_SIZE];
int src, dst;
int bytesRead;
char dstFile[1024];
if (argc != 3)
{
printf("argument error\n");
printf("usage: ./a.out src dest\n");
}
if ((src = open(argv[1], O_RDONLY)) == -1)
{
printf("Error accessing source file.\n");
exit(1);
}
strcat(dstFile, argv[2]);
strcat(dstFile, argv[1]);
if ((dst = open(dstFile, O_WRONLY | O_CREAT | O_TRUNC, 0644)) == -1)
{
printf("Error accessing destination file. %s\n", dstFile);
exit(1);
}
while ((bytesRead = read(src, buffer, BUF_SIZE)) > 0)
{
write(dst, buffer, bytesRead);
}
close(src);
close(dst);
return 0;